PROJECT SUMMARY Stress is a leading cause of functional hypothalamic amenorrhea and infertility. Amenorrhea is associated with cardiovascular disease, osteoporosis, and mental health, therefore elucidation of the mechanisms by which stress suppresses gonadotropin secretion may provide new avenues to protect against chronic illnesses. Metabolic stress occurs in healthy people as well as in several disease states. Insulin-induced hypoglycemia (IIH) is a reliable, repeatable and quantifiable model of acute metabolic stress that suppresses pulsatile luteinizing hormone (LH) secretion; however, the mechanisms that mediate the suppression of LH are not known. This proposal will use genetic, pharmacologic and molecular approaches to test the hypothesis that urocortin 2 cells in the paraventricular nucleus (PVN) are innervated by brainstem norepinephrine neurons, and project onto and inhibit kisspeptin neurons in the arcuate nucleus to suppress pulsatile LH secretion in IIH. In Aim 1, we will determine if urocortin 2 cells in the PVN receive anatomical and functional input from brainstem norepinephrine neurons during IIH. In Aim 2, we will determine if kisspeptin cells receive anatomical and functional input from urocortin 2 neurons in the PVN during IIH. In Aim 3, we will characterize the effects of urocortin 2 on ARC kisspeptin neuron function in an immortalized hypothalamic kisspeptin-expressing cell line. This project will examine the form and function of a brainstem-PVN-arcuate nucleus neural circuit to inhibit pulsatile LH secretion during metabolic stress. These experiments will test an innovative hypothesis involving urocortin 2 signaling that will advance our knowledge of integrated stress responses, regulation of gonadotropin secretion, and provide the applicant training in critical skills that will be necessary for a successful career in academic research.